The
Autonomous Extravehicular Activity Robotic Camera Sprint (AERCam Sprint)
is an experiment planned to demonstrate the use of a prototype free-flying
television camera that could be used for remote inspections of the exterior
of the International Space Station.

The AERCam Sprint free-flyer
is a 14-inch diameter, 35-pound sphere that contains two television
cameras, an avionics system and 12 small nitrogen gas-powered thrusters.
The sphere, which looks like an oversized soccer ball, was released
by Mission Specialist Winston Scott during the STS-87 spacewalk and
flew
freely in the forward cargo bay for about 30 minutes. The free-flyer
was remotely controlled by Pilot Steve Lindsey from the Shuttle's aft
flight deck using a hand controller, two
laptop computers and a window-mounted antenna. The AERCam is designed
to fly very slowly at a rate of less than one-quarter of a foot per
second. Remote control of the AERCam is performed through two-way Ultra
High Frequency radio communications, with data regarding the status
of the free-flyer's systems transmitted back to the operator. Television
images are transmitted back to the operator via a one-way S-band communications
link. During the experiment operations, live television images also
will be relayed via Columbia to Mission Control. Two miniature color
television cameras are mounted on the free-flyer, one with a 6 millimeter
lens and another with a 12 millimeter lens. The exterior of the free-flyer
sphere is covered with a sixth-tenths of an inch-thick layer of Nomex
felt to cushion any inadvertent contact with a spacecraft surface and
prevent damage.

Most of the free-flyer's systems
are derived from the development of the Simplified Aid for EVA Rescue
(SAFER) backpack. The AERCam's thrusters, basic avionics, solid-state
rate sensors, attitude hold electronics, nitrogen tank and hand controller
are identical to those used on the SAFER. The AERCam thrusters, however,
produce eight-hundredths of a pound of thrust while the SAFER thrusters
produced eight-tenths of a pound of thrust.

The free-flyer is powered by
lithium batteries. Its electrical supply and nitrogen supply are designed
to last at least seven hours, the maximum length of a normal spacewalk.
The AERCam sphere has a small floodlight built in that is identical
to floodlights used on the helmets of spacesuits. Spaced equally around
the sphere also are six, small, flashing yellow light-emitting diode
lights that make the free-flyer visible to the operator in darkness.

The front of the sphere is
marked by stripes and arrows while the back is marked by dots. These
markings assist the operator in determining the orientation of the AERCam.
A small fabric strap on the sphere serves as a handhold for the spacewalker
while deploying and retrieving the free flyer.